RFR: JDK-8215550: Debugger does not work after reattach

[Gary Adams]

As far as I can tell, the quit and exit commands are only handled locally
on the debugger side of the connection. There is no packet sent to the
libjdwp agentlib.

On 1/29/19, 12:17 PM, Chris Plummer wrote:
> Hi Gary,
>
> When the "exit" or "quit" is done, aren't all threads resumed at that 
> point, and shouldn't that result in the command loop being unblocked?
>
> thanks,
>
> Chris
>
> On 1/29/19 8:09 AM, Gary Adams wrote:
>> Significant protections are put in place to protect the commandLoop
>> from multiple events that that have a suspend-all policy. The
>> commandLoop uses a special block variable to ensure only
>> a VirtualMachine or ThreadReference call to resume() will unblock
>> the commandLoop. See
>>
>>   src/jdk.jdwp.agent/share/native/libjdwp/eventHelper.c
>>
>> In this particular bug report, the user was stopped at a breakpoint
>> when they sent the "exit" command. The same effect can be produced
>> with a "quit" command or any killing of the debugger process.
>>
>> When the second session is started the commandLoop is still blocked,
>> so a new breakpoint will never be dequeued from the commandQueue.
>>
>> The proposed workaround will ensure the commandLoop is unblocked
>> when a new session is started.
>>
>>   Issue: https://bugs.openjdk.java.net/browse/JDK-8215550
>>   Webrev: http://cr.openjdk.java.net/~gadams/8215550/webrev.00/
>>
>> All testing has been done by manually replicating the reported
>> command sequences. I'll see if an existing breakpoint test can be
>> enhanced to cover this scenario.
>
>
>